1. Field of the Invention
The invention relates to a camera adapter having a camera holder and an optical adapter as well as to the camera holder and the optical adapter themselves.
2. Description of the Related Art
Special phototubes that have a coupling-out device in the observer's binocular tube for photographic recordings are used in microscopy. However, it is not always readily possible to arrange the coupling-out device in the observer's binocular tube. For example, pivoting tubes often are used in microsurgery to adapt a surgical microscope ergonomically to the surgical situation. However, it is not possible to use a coupling-out device in the binocular tube in the case of pivoting tubes. Therefore, a compromise usually is selected at present for stereomicroscopes, for instance surgical microscopes, namely a so-called TV adapter which is provided with additional optics. This adapter is adapted to a coupling-out device in the region of the parallel beam path between the magnification changer and the binocular tube.
A TV adapter is highly suitable for recording television images, but is less suitable for use with a digital photographic apparatus. Therefore, the use of a TV adapter is a compromise that entails some disadvantages. For example, pupil adaptation is not optimal. As a result, in an image that has been recorded using the photographic apparatus, the field of view may be cut or such significant zooming may be required that only a small part of the object field can be recorded. On the other hand, the image quality criteria for high-resolution camera chips in digital photographic apparatuses with TV adapters generally are not met since they are adapted to the resolution of TV cameras, which is considerably lower than that of photographic apparatuses. In other words, the optics of TV adapters will scarcely meet the demands imposed by a digital photographic apparatus.
Another problem of prior art camera adapters used for surgical microscopes resides in the mechanical interface, and specifically in the manner in which the photographic apparatus is fixed to the camera adapter. This problem relates both to conventional camera adapters and to TV adapters. The mechanical interfaces currently used by many camera adapter manufacturers are a filter thread or a bayonet on the outer end of the camera objective. However, such mechanical interfaces are generally not standardized and often are changed with the yearly model change by the manufacturer. Under certain circumstances, such an interface may even be dispensed with entirely in the photographic apparatus. There are many products that do not have a filter thread or a bayonet, particularly in the field of compact digital cameras. Nevertheless, many camera adapter manufacturers accept the risks that have been mentioned and arise when models are changed and equip their camera adapters with mating pieces that match special bayonets or special filter threads and to which cameras having corresponding filter threads or bayonets can be fixed. However, the choice of cameras that can be fixed to such a camera adapter is limited due to the many different filter threads and bayonets that may result, for example, solely from different objective diameters.
It was proposed, therefore, to use holders for fastening photographic apparatuses to microscopes or telescopes. The holders use the stand thread present on virtually all photographic apparatuses and has undergone substantial standardization to fix the photographic apparatus. Stand threads are durable, that is to say the interface is generally retained as a constant variable when models are changed, and are offered by virtually all camera manufacturers on the underside of the camera. Filter threads or bayonets are arranged centrically with respect to the objective. However, the stand threads have a translatory offset with respect to the objective in at least two directions. Therefore, complicated alignment of a photographic apparatus, which is fixed directly or indirectly to an optical observation device by means of the stand thread, with respect to the photoadapter is necessary.
Apparatuses for fixing photographic apparatuses to microscopes, binoculars and telescopes using the stand thread are described, for example, in JP 2006-39191A, JP 2002-277953A, GB 1 215 710, US 2002/0197075 A1 and U.S. Pat. No. 2,990,759. All of these apparatuses have adjusting devices that can be used to compensate for an offset between the objective and the stand thread.
Therefore, a first object of the invention is to provide a holder for camera adapters that can be used advantageously to fix photographic apparatuses to a camera adapter or, if necessary, to an optical observation device using the stand thread.
A second object of the invention is to provide an optical adapter that can be used in camera adapters and avoids the disadvantages mentioned with respect to the TV adapters.
A third object of the invention is to provide an advantageous camera adapter.